Initial stages of lichen hydration observed by proton magnetic relaxation

Abstract

The hydration of selected lichens (Cladonia mitis, Cladonia bellidiflora, Cetraria islandica, Parmelia saxatilis, and Xanthoria parietina) was investigated using gravimetry and proton magnetic free induction decays (FIDs).The hydration from gaseous phase and dehydration to gaseous phase showed first-order kinetics. The amount of water which was non-removable in the air-dry state (relative humidity p\p ! l 9 %) did not depend significantly on the lichen species and was found to be 5n6p1n0 % of the d. wt.The proton FID Gaussian component from the solid matrix of thallus structure, and two (or, depending on lichen species, one averaged) liquid signals coming from water tightly bound on the surface of thallus solid matrix and from loosely bound or free water, were recorded. The bound-water component was distinguished by its motional properties and by its proximity to endogenous paramagnetic centres present in solid matrix (presumably PS II reaction centres of the photobiont). Mild dehydration (from gaseous phase) could completely remove the loosely bound water fraction, leaving the system below the water percolation threshold and below the water clustering point, emphasizing the passivity of lichen response to desiccation shock. In the species in which the one average liquid component was recorded, bound water behaved similarly.The hydration at which free water pool vanishes (∆M\m ! ) and the relative (scaled to water) proton densities of solid matrix of lichen (β) were evaluated for all lichens investigated.

Maturation Process of Photosynthetic Membranes Observed by Proton Magnetic Relaxation and Sorption Isotherm

“…This value is close to the value obtained for the other photosynthetic membrane lyophilizates [14], for lichen thalli, and for numerous solid tissues such as dentine, dental enamel, the shells of moluscs, bark and bast (e.g. [17] and references therein). Thus, we assigned the immobilized proton component S 0 to (i) the solid matrix of the wheat thylakoid lyophilizate.…”

“…3. The 1/e-value instead of the one-half value for solid Gaussian curve allows one a direct comparison between the several characteristic time constants describing FID [16][17][18]. This value is close to the value obtained for the other photosynthetic membrane lyophilizates [14], for lichen thalli, and for numerous solid tissues such as dentine, dental enamel, the shells of moluscs, bark and bast (e.g.…”

“…This resembles the tightly bound water signal for the photosynthetic membrane lyophilizates [14], for lichen thalli, and for solid tissues such as dentine, dental enamel, the shells of moluscs, bark and bast (e.g. [17] and references therein), as well as that of the control porous glass [23]. Thus, we assigned the L 1 signal component to tightly bound water (presumably first hydration shell).…”

Initial Phases of DNA Rehydration by NMR and Sorption Isotherm

“…The value of the spin-spin relaxation time for solid is close to that value for the solid matrices of several dry microheterogeneous biological systems (e.g. model DGDG membranes [12], photosynthetic membranes [13], bark and bast [14], wheat seed [15], lichen thallus [11,[16][17][18][19], dentine and dental enamel [20]). Moreover, similar values of spin-spin relaxation time are recorded for dry solid polymer matrices [21].…”

“…Proton FID time for the L 1 fraction resembles that for the immobilized (tightly bound) water signal of photosynthetic membranes [13], bark and bast [14], wheat seed [15], lichen thallus [11,[16][17][18][19], dentine and dental enamel [20], and of the controlled pore glasses [22].…”